1. Field of the Invention
The present invention relates to a method for producing a rubber composition. The rubber composition is useful as a raw material of a vulcanized rubber excellent in low thermogenic performance.
2. Description of the Related Art
In recent years, developments of fuel-efficient tires have been actively made in the tire industry from the viewpoint of energy saving. It is said that for the fuel-efficient tire developments, it is indispensable to improve, in particular, the low thermogenic performance of respective rubber regions of tire treads that are obtained by vulcanization.
As a technique for improving a vulcanized rubber in low thermogenic performance, Patent Document 1 listed below describes a technique of blending a hydrazide compound and a reinforcing filler into a rubber composition as a raw material.
Patent Document 2 listed below describes a technique that is a method of kneading a rubber composition containing a raw material polymer, a hydrazide compound and a carbon black, in which the raw material polymer and the hydrazide compound are earlier kneaded, and then the carbon black is added thereto to knead the resultant mixture.
Patent Document 3 listed below describes a technique of using, for a tire tread region of a pneumatic tire, a rubber composition in which 0.05 to 5 parts by mass of a specific hydrazide compound is blended into 100 parts by mass of a rubber component.
Patent Document 4 listed below describes a technique of mixing a natural rubber and a carbon black with each other in a first kneading step, and then charging/blending a dihydrazide compound into the mixture in a second kneading step.